It’s VOLUNTARY. It’s not slavery. No one is making them do this. They also get paid (though not enough). They also get reduced sentences. In California they also may get their record expunged. Read the article.
Today, more than 76 percent of incarcerated workers surveyed by the Bureau of Justice Statistics say that they are required to work or face additional punishment such as solitary confinement, denial of opportunities to reduce their sentence, and loss of family visitation.
Do you know what you call someone that gets punished if they don't work? It's not volunteer.
Indentured servitude was voluntary. Im sure if you were alive before we considered that slavery you'd be an apologist for that form of slavery as well.
They can sit in a cell or they can be rented as property and get to go outside.
That's not exactly a choice, you can do nothing or something, and you should be grateful for the something even if it's slavery.